This proposal seeks two years of support to conduct secondary analyses using data from Project Family, a gender-balanced panel study of 429 rural youths and their families constituted in 1993 when students entered the sixth grade. Adolescents and their parents were interviewed and observed in structured interactions on six occasions across seven years. Guided by the social development model and a developmental psychopathology perspective, this study will examine the relative (additive) and interactive effects of conduct problems and depressive symptoms on substance use throughout adolescence and on problem use at age 18. The study also will examine the extent to which social developmental processes during adolescence mediate the effects of psychopathology on substance use and problem use. Further, gender differences in the hypothesized relations will be tested, and background variables, such as parental psychopathology, will be included in the analyses. Findings from the study will inform drug abuse prevention for adolescents by elucidating variables that may be used for the early identification of at-risk individuals in need of selective prevention services, and by identifying malleable social developmental processes that mediate the link between psychopathology and problem use.